SPID#: 58 Studies are being conducted with apes in two behavioral domains (1) gestural communication, and (2) cooperative interactions. In the domain of gestural communication, the gestural signals of a complex social group of chimpanzees at the Yerkes Field Station was documented. This is the same group that has been documented on three previous occasions (1983, 1987, 1991) and so the longitudinal data base was significantly enhanced. In addition, the recent establishment of a new chimpanzee group at Yerkes allowed a very important point of comparison. Also, in an experimental study one individual was removed from the group, taught a novel gesture, returned to the group, and the group observed for signal acquisition. Using longitudinal comparisons across the four time points, comparison between two different groups, and experimental data, the focus is on the specific learning processes involved. In the domain of cooperation, some socially-housed chimpanzee dyads were presented with a task in which cooperation was required. The basic idea was to observe how they coordinate their behavior in these situations and how they communicate about the task. Determining precisely how chimpanzees transfer information socially in these two behavioral domains is important because it will help to elucidate the nature of the proximate mechanisms by means of which this species takes advantage of the knowledge of conspecifics.